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Gel compositions for topical administrationRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Preparations Characterized By Special Physical Form, Matrices, Synthetic PolymerGel compositions for topical administration description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060292223, Gel compositions for topical administration. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims the benefit of U.S. Provisional Patent Application No. 60/691,441, filed Jun. 16, 2005, the entire disclosure of which is incorporated by reference herein. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention is directed to gel compositions for topical administration, as well as to methods of making and administering the same. The gel compositions contain a gelation promoter which at least partially solubilizes an active ingredient and which gels a polymeric component therein. [0004] 2. Related Background Art [0005] Conventional semi-solid topical preparations comprise single-phase systems or two-phase emulsified systems. As used herein, the term "semi-solid" is understood to refer to the rheological properties of the compositions themselves, such that the compositions will flow under an applied force but will remain in situ following application to any accessible body surface. [0006] Single-phase semi-solid systems may be hydrophobic ointments or hydrophilic gels. Two-phase semi-solid systems are emulsions, in which the continuous phase may be hydrophobic, as in a water-in-oil emulsion, or hydrophilic, as in an oil-in-water emulsion. For a pharmacologically active component of such preparations, it is preferred that such component is substantially in solution rather than in suspension within the preparation, due to the greater release rate of the pharmacologically active component from solution. For a pharmacologically active component whose aqueous solubility is relatively low, for example, where less than 25% of the total loading may be solubilized within an aqueous preparation, a hydrophobic preparation or a preparation with a hydrophobic phase is desirable. Thus, pharmacologically active components of low aqueous solubility may be solubilized within a hydrophobic ointment or a two-phase emulsion system in which it is primarily in solution within the oil phase. [0007] A problem encountered with conventional ointments and water-in-oil hydrophobic preparations is that they can be greasy and/or extremely difficult to apply due to the significant hydrophobic oil or wax component. If applied onto the skin, such preparations tend to stain clothing and are preferably used only where the skin condition is extremely dry. [0008] Oil-in-water preparations, sometimes referred to in the art as "vanishing" creams, overcome the problems of greasiness and staining of clothing. However, pharmacologically active components of lower aqueous solubility are solubilized within the internal oil emulsion phase of such preparations. They must, therefore, partition across the external aqueous (continuous) phase to reach their site of action. This may restrict release and subsequent topical bioavailability of the pharmacologically active component from such preparations. [0009] Conventional gel preparations overcome many of the foregoing problems. As used herein, the term "gel" is understood to be a semi-solid matrix of particles interpenetrated by a liquid, in which the structural coherent matrix contains a high portion of liquid, usually water. Such gels comprise a single phase. Where the liquid phase is water, or substantially water, pharmacologically active components of low aqueous solubility will be present substantially in suspension; thus release and subsequent bioavailability may be restricted. [0010] Known pharmaceutical gel compositions for topical administration conventionally comprise polymers, for example, modified cellulose ethers, natural gums or polymers containing pendant carboxylic acid groups, or their esters, or having pendant anhydrides of dicarboxylic acid groups, or mixtures thereof. Carboxylic acid polymers in aqueous systems are conventionally neutralized from a starting pH of about 2.5 to 3.5 to a pH of 4.0 or more in order to achieve gelation. Conventional neutralizers comprise sodium hydroxide, potassium hydroxide, ammonium hydroxide, arginine, aminomethyl propanol, tetrahydroxypropyl ethylenediamine, triethanolamine, tromethamine, PEG-15 cocamine, diisopropanolamine or triisopropanolamine. However, all polymer gel compositions, exemplified by the foregoing, will require the presence of a solubilizing agent to substantially solubilize a pharmacologically active agent of low aqueous solubility. For this reason, known pharmaceutical gel compositions for topical administration may conventionally contain an alcoholic component, ethanol, as a solubilizer. This may also present difficulties in certain clinical conditions such as dry skin. [0011] More specifically, known pharmaceutical gel compositions for external application to the skin comprise Estrogel.RTM. (Solvay, US) and Sandrena.RTM. (Organon, Netherlands). Estrogel.RTM. is a hydro-ethanolic gel containing 0.06% estradiol; the excipients are ethanol, Carbomer 934 and triethanolamine, the balance being purified water. Sandrena.RTM. is another hydro-alcoholic gel containing 0.1% estradiol; its excipients are Carbomer 934, sodium hydroxide, propylene glycol, ethanol and water. Clearly, the base of these pharmaceutical gel compositions is a mixture of water and ethanol. The ethanol is intended to increase estrogen solubility in the gel and assist absorption into the stratum corneum. [0012] EP-B-435200 in the names of Nitto Denko Corp. and Teikoku Hormone Mfg. Co. relates to an estrogen-containing gel for external administration to the skin. The gels are covalently cross-linked using, for example, a titanium or aluminum chelate compound. There is no disclosure or suggestion that a gelation promoter might be selected to both solubilize the estrogen and to gel the polymer. [0013] EP-B-813412 in the name of Laboratoire Innothera relates to vaginal estradiol-containing gels comprising a polymer that has been gelled by neutralization by a conventional neutralizer. There is no disclosure or suggestion that a gelation promoter might be selected to both solubilize the estrogen and to gel the polymer in a non-aqueous or substantially non-aqueous environment. [0014] DE-A-199 45 522 in the name of Hexal AG relates to compositions for topical administration. The compositions are oil-in-water emulsions containing a polymer as a thickening agent. The compositions are erroneously described in DE-A-199 45 522 as gels. There is no disclosure or suggestion that a gelation promoter might be selected to both solubilize the estrogen and to gel the polymer. [0015] Accordingly, pharmaceutical gel compositions for topical administration which do not suffer from the deficiencies of conventional semi-solid topical compositions are highly desirable. SUMMARY OF THE INVENTION [0016] The present invention is directed to a pharmaceutical gel composition for topical administration comprising (a) at least one pharmacologically active agent in an amount of about 0.00001% to about 10% by weight of the composition; (b) at least one hydrogen-bonding gelation polymer; and (c) at least one gelation promoter in an amount effective to at least partially solubilize the pharmacologically active agent and to gel the polymer, wherein at least a portion of the pharmacologically active agent is dissolved in the composition at 15.degree. C. The formation of a gel from one or more suitable hydrogen-bonding gelation polymer(s) capable of viscosity enhancement in the presence of at least one gelation promoter capable of both causing gelation promotion and at least partial solubilization of the at least one pharmacologically active agent is desirable for both improved release rate of the drug from the product and for a more elegant water-washable product. In preferred embodiments, the hydrogen-bonding gelation polymer is present in an amount sufficient to form a gel with a viscosity ranging from about 25 Pas to about 1000 Pas at 20.degree. C. In other preferred embodiments, at least 25%, more preferably at least 50%, and most preferably at least 75% of the pharmacologically active agent is dissolved at 15.degree. C. In certain embodiments of the present invention, the at least one pharmacologically active agent is selected from agents that are cosmetically, therapeutically or prophylactically active in the following cosmetic, therapeutic and prophylactic areas: gynecology, urinary tract disorders, infection control, inflammatory conditions, central nervous system disorders and skin disorders. In certain embodiments, the at least one hydrogen-bonding gelation polymer is a homopolymer, copolymer or interpolymer having pendant carboxylic acid groups, having pendant anhydrides of dicarboxylic acid groups, or having both (or esters of any thereof). In certain embodiments, the at least one gelation promoter is at least one polyhydric alcohol, at least one polyglycol or a combination thereof. In certain embodiments, the gelation promoter comprises an aqueous solution of a gelation promoter. [0017] The present invention is further directed to a method of making pharmaceutical gel compositions for topical administration comprising the step of admixing at least one pharmacologically active agent in an amount of about 0.00001% to about 10% by weight of the composition, at least one hydrogen-bonding gelation polymer, and at least one gelation promoter or aqueous solution thereof in an amount effective to at least partially solubilize the pharmacologically active agent and to gel the polymer to form the pharmaceutical gel composition, wherein at least a portion of the pharmacologically active agent is dissolved in the composition at 15.degree. C. In a preferred embodiment, the admixing comprises (a) at least partially solubilizing the pharmacologically active agent in the gelation promoter (or in the aqueous solution of the gelation promoter) to form an at least partially solubilized pharmacologically active agent preparation; and (b) combining the at least partially solubilized pharmacologically active agent preparation with the hydrogen-bonding gelation polymer to form the pharmaceutical gel composition. [0018] The present invention is still further directed to a pharmaceutical gel composition made according to the present inventive method and to a method of administering a pharmaceutical gel composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0019] As used herein, the term "topical administration" refers to administration onto any accessible body surface of any human or animal species, preferably the human species, for example, the skin or mucosal epithelia such as nasal or rectal epithelia. In certain embodiments of this invention, "topical" refers to an external application to a skin surface. [0020] As used herein, "pharmacologically active agent" or "agent" or "drug" or "active agent" or "active ingredient", etc., refers to any agent capable of defending against, or treating, a disease or cosmetic state in the human or animal body, or a prodrug thereof. Such pharmacologically active agents may be organic or inorganic and may be prophylactically or therapeutically active. Alternatively or additionally, such pharmacologically active agents may be cosmetically active. As used herein, "prophylactically active" refers to an agent's (or its prodrug's) effectiveness in defending against a disease state in the human or animal body, preferably the human body. As used herein, "therapeutically active" refers to an agent's (or its prodrug's) effectiveness in treating a disease state in the human or animal body, preferably the human body. As used herein, "cosmetically active" refers to an agent's (or its prodrug's) effectiveness in defending against or treating a cosmetic condition in or on the human or animal body, preferably the human body. [0021] Without being bound by theory, as used herein, "hydrogen-bonding gelation polymer" refers to polymers, which are capable of taking part in hydrogen bonding with the functional groups of a gelation promoter. Such polymers may also be capable of gelation by neutralization but, in the compositions of the present invention, gelation is achieved by hydrogen-bonding. As used herein, "hydrogen-bonding" refers to a non-covalent bond between hydrogen and another atom, usually nitrogen or oxygen. Hydrogen bonding does not involve the sharing of electrons between the bonded atoms and, therefore, does not satisfy the valence of either atom. Continue reading about Gel compositions for topical administration... 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